I now call him darth leper. The most useful thing I ever had on a keyring was a bottle opener, though this does increase the bulk of the keyring- in the wrong trousers it can give the appearance of some kind of hernia..

A miniature compact mirror
A bottle opener in the shape of a dolphin [Dontcha just love crackers?]
One half of a 'Best Friends' type keyring from years ago in the form of one of the 'Me to You' bears...
A scooby thing made by my sister :)
A rugby ball keyring given to me on a bad day to cheer me up
And a purple leopard skin heart keyring

In addition to being on one of those neckchains that my best friend gave me to stop me losing my keys in halls last year...